These investigators are largely directed toward elucidation of the acute and chronic changes in the production, composition and metabolism of circulating lipoproteins (primarily very low density lipoproteins) during experimental diabetes in the rat, and on the direct role of insulin on these processes. The studies include: assessment of plasma lipoprotein lipid and apoprotein alterations in acute streptozotocin-induced diabetes, when major increases in total plasma lipids are not yet evident; reversibility of apolipoprotein changes following a single dose of insulin; and altered lipoprotein composition and insuling-reversibility in chronic (7-12 days) experimental diabetes, when significant increases in plasma lipids are evident. Metabolism of lipoproteins will be assessed both in vivo (fractional clearance rates in normal and diabetic rats) and in the perfused heart as a model for membrane-supported lipoprotein lipase. The extent of recognition and metabolism of the remnant particles resulting from myocardial utilization of VLDL triglyceride will be determined by analyses of effects on fatty acid and cholesterol biosynthesis in cultured rat hepatocytes. Acute and chronic changes in total and heparin-releasable lipoprotein lipase activity and enzyme protein induced by diabetes and potenmtial reversibility by insulin will also be assessed in the perfused heart model.